Apparatus and method for supporting unicast transmission between user equipments in wireless communication system

ABSTRACT

The disclosure relates to a 5th generation (5G) or a pre-5G communication system provided to support a higher data transfer rate than a system after a 4th generation (4G) communication system such as long term evolution (LTE). An operation method of a terminal in a wireless communication system includes: obtaining an RLC transmission mode and RLC configuration information in the process of determining a V2X service requiring configuration of a unicast session and configuring the unicast session with another terminal; if the terminal is determined to be in the coverage of a base station, receiving an RLC transmission mode and RLC configuration information from the base station; and if it is determined that the terminal is not located in a base station coverage, obtaining a pre-configured unicast session and pre-configured RLC configuration information for each RLC transmission mode, which is mapped to a V2X service.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 National Stage of International ApplicationNo. PCT/KR2019/013235, filed Oct. 8, 2019, which claims priority toKorean Patent Application No. 10-2018-0120063, filed Oct. 8, 2018, andKorean Patent Application No. 10-2019-0074108, filed Jun. 21, 2019, thedisclosures of which are herein incorporated by reference in theirentirety.

BACKGROUND 1. Field

The disclosure relates generally to a wireless communication system and,more specifically, relates to an apparatus and method for supportingtransmission or reception of a packet between terminals in a unicastscheme in a wireless communication system.

2. Description of Related Art

In order to meet wireless data traffic demands increasing aftercommercialization of 4G communication system, efforts to develop animproved 5G communication system or a pre-5G communication system havebeen made. For this reason, the 5G communication system or the pre-5Gcommunication system is called a beyond 4G network communication systemor a post-LTE system.

The 5G communication system is being considered to be implemented in asuper-high frequency (mmWave) band (e.g., about 60 GHz band) to achievea higher data transfer rate. To reduce the path loss of radio waves andincrease the transfer distance of radio waves in a super-high frequencyband, technologies including beamforming, massive multiple-input andmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antennas,analog beamforming, and large scale antennas have been discussed for the5G communication system.

Further, technologies such as an evolved small cell, an advanced smallcell, a cloud radio access network (cloud RAN), an ultra-dense network,device to device communication (D2D), a wireless backhaul, a movingnetwork, cooperative communication, coordinated multi-points (CoMP), andreceived interference cancellation have been developed for the 5Gcommunication system to improve the system network.

In addition, advanced coding modulation (ACM) schemes such as hybrid FSKand QAM modulation (FQAM) and sliding window superposition coding(SWSC), and advanced access technologies such as filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) have been developed for the 5G system.

In the 5G system, various schemes for determining wireless resourceshave been discussed. For example, a direct communication scheme for avehicle-to-everything (V2X) terminal has been proposed. Further, variousdiscussions for shortening communication time, increasing reliability,and more efficiently supporting a direct communication between terminalsare proceeding.

SUMMARY

On the basis of the discussions as described above, the disclosureprovides an apparatus and method for supporting vehicle communicationservice and data transmission which accomplish high reliability andlow-latency requirements, through a method of performing directcommunication between terminals in a unicast scheme in a vehiclecommunication system.

According to various embodiments, an operation method of a terminal in awireless communication system includes: transmitting, by the terminal,an RLC transmission mode configuration request to a base station toobtain an RLC transmission mode and RLC configuration information in theprocess of determining a V2X service requiring configuration of asidelink unicast session and configuring the unicast session withanother terminal; receiving the RLC transmission mode and RLCconfiguration information from the base station; and if it is determinedthat the terminal is not located in a base station coverage, obtainingpre-configured RLC configuration information for each RLC transmissionmode, which is mapped to a V2X service profile for which the sidelinkunicast session is configured.

According to various embodiments, a terminal apparatus in a wirelesscommunication system includes a transceiver unit and at least oneprocessor functionally coupled to the transceiver unit. The at least oneprocessor is configured to: if the terminal apparatus is determined tobe in the coverage of a base station, transmit sidelink unicast sessioninformation, and an RLC transmission mode and RLC configurationinformation request message to the base station; and receive an RLCtransmission mode and RLC configuration information to be applied to asidelink unicast session, from the base station, so as to control theterminal apparatus to perform sidelink unicast transmission orreception. The at least one processor is configured to: if it isdetermined that the terminal apparatus is not located in a base stationcoverage, obtain pre-configured RLC transmission mode and RLCconfiguration information, which is mapped to a V2X service profile of asidelink unicast session, so as to control the terminal apparatus toperform sidelink unicast transmission or reception.

An apparatus and method according to various embodiments provides amethod allowing transmission or reception of a packet in a unicastscheme between terminals in a vehicle communication system, therebyaccomplishing reliability and low-latency requirements in vehiclecommunication.

Effects which can be acquired by the disclosure are not limited to theabove described effects, and other effects that have not been mentionedmay be clearly understood by those skilled in the art from the followingdescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system according to variousembodiments;

FIG. 2 illustrates a configuration of a base station in a wirelesscommunication system according to various embodiments;

FIG. 3 illustrates a configuration of a terminal in a wirelesscommunication system according to various embodiments;

FIGS. 4A to 4C illustrate a configuration of a communication unit in awireless communication system according to various embodiments;

FIG. 5 illustrates direct communication between terminals by a unicastscheme according to various embodiments;

FIG. 6 illustrates configuring a session for unicast transmissionbetween terminals according to various embodiments;

FIGS. 7A to 7F illustrate a terminal-to-base station signaling procedurefor configuring an RLC transmission mode for unicast transmissionbetween terminals according to various embodiments;

FIG. 8 illustrates releasing a session for unicast transmission betweenterminals according to various embodiments;

FIG. 9 illustrates an operation of a base station for unicasttransmission between terminals according to various embodiments;

FIG. 10 illustrates an operation of a terminal which is in anRRC-connected state, the operation being performed forterminal-to-terminal unicast transmission according to variousembodiments;

FIG. 11 illustrates an operation of a terminal which is in anRRC-disconnected state, the operation being performed forterminal-to-terminal unicast transmission according to variousembodiments;

FIGS. 12A to 12B illustrate a signal flow diagram between a terminal anda base station which exchange RAT information according to a V2X servicetype according to various embodiments;

FIG. 13 illustrates an operation of obtaining V2X configurationinformation, based on RAT information according to a V2X service type bya terminal which is in an RRC-connected state, according to variousembodiments;

FIG. 14 illustrates an operation of obtaining V2X configurationinformation, based on RAT information according to a V2X service type bya terminal which is in an RRC-disconnected state, according to variousembodiments; and

FIG. 15 illustrates an operation of processing sidelink unicastconfiguration information by a terminal according to an embodiment.

DETAILED DESCRIPTION

The terms used in the disclosure are merely for the purpose ofdescribing particular embodiments and are not intended to limit thescope of other embodiments. A singular expression may include a pluralexpression unless they are definitely different in a context. Unlessdefined otherwise, all terms used herein, including technical andscientific terms, have the same meaning as those commonly understood bya person skilled in the art to which the disclosure pertains. Such termsas those defined in a generally used dictionary may be interpreted tohave the meanings equal or similar to the contextual meanings in therelevant field of art, and are not to be interpreted to have ideal orexcessively formal meanings unless clearly defined in the disclosure. Insome cases, even the term defined in the disclosure should not beinterpreted to exclude embodiments.

Hereinafter, various embodiments will be described from the perspectiveof hardware. However, various embodiments include a technology that usesboth hardware and software and thus, the various embodiments may notexclude the perspective of software.

Hereinafter, the disclosure relates to an apparatus and method fordetermining wireless resources in a wireless communication system.Specifically, the disclosure includes a technology enabling satisfactionof a QoS level required for a V2X service by supporting unicasttransmission or reception of data on the basis of a method for selectingan RLC transmission mode and obtaining RLC configuration information toperform direct communication between vehicle-to-everything (V2X)terminals through unicast sidelink in a wireless communication system.

In the following description, terms including a term indicating asignal, a term indicating a channel, a term indicating controlinformation, a term indicating network entities, a term indicating anelement of an apparatus, and the like are exemplified for convenience ofexplanation. Accordingly, the disclosure is not limited to the followingterms and other terms having the same technical meaning may be used.

In addition, the disclosure includes terms used in some communicationprotocols (e.g. 3^(rd) Generation partnership project (3GPP)) to explainvarious embodiments, but the terms merely correspond to examples.Various embodiments may be easily modified to be applied to anothercommunication system.

FIG. 1 illustrates a wireless communication system according to variousembodiments. FIG. 1 illustrates a base station 110, a terminal 120, anda terminal 130 as a part of nodes using wireless channels in a wirelesscommunication system. FIG. 1 illustrates only one base station, but thesystem may further include another base station which is the same as orsimilar to the base station 110. FIG. 1 illustrates only two terminals,but the system may further include another terminal which is the same asor similar to the terminals 120 and 130.

The base station 110 is a network infrastructure that provides wirelessconnection to the terminals 120 and 130. The base station 110 has acoverage defined as a particular geographic area based on a distance bywhich the base station 110 can transmit a signal. The base station 110may be called “an access point (AP)”, “an eNodeB (eNB)”, “a 5^(th)generation node”, “a 5G nodeB (gNodeB, gNB)”, “a wireless point”, “atransmission/reception point (TRP)”, or another term having a technicalmeaning equivalent thereto.

Each of the terminals 120 and 130 is a device used by a user andperforms communication with the base station 110 through wirelesschannels. In some cases, at least one of the terminals 120 and 130 maybe operated without involvement of a user. That is, at least one of theterminals 120 and 130 is a device configured to perform machine-typecommunication (MTC) and may not be carried by a user. Each of theterminals 120 and 130 may be called “a user equipment (UE)”, “a mobilestation”, “a subscriber station”, “a remote terminal”, “a wirelessterminal”, “a user device”, or another term having a technical meaningequivalent thereto.

The base station 110 and the terminals 120 and 130 may transmit andreceive a wireless signal in sub 6 GHz bands and millimeter wave(mmWave) bands (e.g. 28 GHz, 30 GHz, 38 GHz, and 60 GHz). To improve thechannel gain, the base station 110 and the terminals 120 and 130 mayperform beamforming. Beamforming may include transmission beamformingand reception beamforming. That is, the base station 110 and theterminals 120 and 130 may give directivity to a transmission signal or areception signal. To this end, the base station 110 and the terminals120 and 130 may select serving beams 112, 113, 121, and 131 through abeam search procedure or a beam management procedure. Communicationafter the serving beams 112, 113, 121, and 131 are selected may beperformed through resources having a quasi-co-located relationship withresources used to transmit the serving beams 112, 113, 121, and 131.

If large-scale characteristics of a channel having transferred a symbolon a first antenna port can be inferred from a channel havingtransferred a symbol on a second antenna port, the first antenna portand the second antennal port may be considered to have a QCLrelationship therebetween. For example, the large-scale characteristicsmay include at least one of delay spread, Doppler spread, Doppler shift,average gain, average delay, and spatial receiver parameter.

FIG. 2 illustrates a configuration of a base station in a wirelesscommunication system according to various embodiments. The configurationillustrated in FIG. 2 may be understood as a configuration of the basestation 110. The term “ . . . unit” or the ending of a word, such as “ .. . or”, “ . . . er”, or the like used hereinafter may indicate a unitof processing at least one function or operation, and this may beembodied by hardware, software, or a combination of hardware andsoftware.

Referring to FIG. 2, a base station includes a wireless communicationunit 210, a backhaul communication unit 220, a storage unit 230, and acontrol unit 240.

The wireless communication unit 210 performs functions for transmittingor receiving a signal through a wireless channel. For example, thewireless communication unit 210 performs a function of conversionbetween a baseband signal and a bit stream according to a physical layerprotocol of the system. For example, when data is transmitted, thewireless communication unit 210 generates complex symbols by encodingand modulating a transmission bit stream. Also, when data is received,the wireless communication unit 210 reconstructs a reception bit streamby demodulating and decoding a baseband signal.

Also, the wireless communication unit 210 up-converts a baseband signalinto a radio-frequency (RF) band signal and then transmits the convertedRF band signal through an antenna, and down-converts an RF band signalreceived through an antenna into a baseband signal. To this end, thewireless communication unit 210 may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, adigital-to-analog convertor (DAC), an analog-to-digital convertor (ADC),and the like. Also, the wireless communication unit 210 may include aplurality of transmission/reception paths. Further, the wirelesscommunication unit 210 may include at least one antenna array configuredby multiple antenna elements.

In view of hardware, the wireless communication unit 210 may beconfigured by a digital unit and an analog unit, and the analog unit mayinclude a plurality of sub-units according to operating power, operatingfrequency, etc. The digital unit may be implemented by at least oneprocessor (e.g. digital signal processor (DSP)).

The wireless communication unit 210 transmits and receives a signal, asdescribed above. Accordingly, the entirety or a part of the wirelesscommunication unit 210 may be called “a transmission unit(transmitter)”, a reception unit (receiver)”, or “a transceiver unit(transceiver)”. Also, in the following description, transmission andreception through a wireless channel may be understood to include theaforementioned processing of the wireless communication unit 210.

The backhaul communication unit 220 provides an interface performingcommunication with other nodes within a network. That is, the backhaulcommunication unit 220 converts, into a physical signal, a bit streamtransmitted from the base station to another node, for example, anotheraccess node, another base station, a higher node, a core network, etc.,and converts a physical signal received from another node into a bitstream.

The storage unit 230 stores data such as a basic program, an applicationprogram, and configuration information for the operation of the basestation. The storage unit 230 may be configured as a volatile memory, anon-volatile memory, or a combination of a volatile memory and anon-volatile memory. The storage unit 230 provides stored data inresponse to a request of the control unit 240.

The control unit 240 controls overall operations of the base station.For example, the control unit 240 transmits and receives a signalthrough the wireless communication unit 210 or the backhaulcommunication unit 220. Further, the control unit 240 records and readsdata in and from the storage unit 230. In addition, the control unit 240may perform functions of a protocol stack required in a communicationprotocol. According to another embodiment, the protocol stack may beincluded in the wireless communication unit 210. To this end, thecontrol unit 240 may include at least one processor.

According to various embodiments, the control unit 240 may transmitradio resource control (RRC) configuration information to the terminal110. For example, the control unit 240 may control the base station toperform operations according to various embodiments described later.

FIG. 3 illustrates a configuration of a terminal in a wirelesscommunication system according to various embodiments. The configurationillustrated in FIG. 3 may be understood as a configuration of theterminal 120 or 130. The term “ . . . unit” or the ending of a word,such as “ . . . or”, “ . . . er”, or the like used hereinafter mayindicate a unit of processing at least one function or operation, andthis may be embodied by hardware, software, or a combination of hardwareand software.

Referring to FIG. 3, a terminal includes a communication unit 310, astorage unit 320, and a control unit 330.

The communication unit 310 performs functions for transmitting orreceiving a signal through a wireless channel. For example, thecommunication unit 310 performs a function of conversion between abaseband signal and a bit stream according to a physical layer protocolof the system. For example, when data is transmitted, the communicationunit 310 generates complex symbols by encoding and modulating atransmission bit stream. Also, when data is received, the communicationunit 310 reconstructs a reception bit stream by demodulating anddecoding a baseband signal. Also, the communication unit 310 up-convertsa baseband signal into an RF band signal and then transmits theconverted RF band signal through an antenna, and down-converts an RFband signal received through an antenna into a baseband signal. Forexample, the communication unit 310 may include a transmission filter, areception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC,and the like.

Also, the communication unit 310 may include a plurality oftransmission/reception paths. Further, the communication unit 310 mayinclude at least one antenna array configured by multiple antennaelements. In view of hardware, the communication unit 310 may beconfigured by a digital circuit and an analog circuit (e.g. radiofrequency integrated circuit (RFIC)). The digital circuit and the analogcircuit may be implemented as a single package. Also, the communicationunit 310 may include a plurality of RF chains. Further, thecommunication unit 310 may perform beamforming.

Also, the communication unit 310 may include different communicationmodules to process signals having different frequency bands. Further,the communication unit 310 may include a plurality of communicationmodules to support a plurality of different radio access technologies.For example, the different radio access technologies may includeBluetooth low energy (BLE), wireless fidelity (Wi-Fi), WiFi gigabyte(WiGig), a cellular network (e.g. long term evolution (LTE), and thelike. Further, the different frequency bands may include a super highfrequency (SHF) (e.g. 2.5 GHz and 5 GHz) band and a millimeter (mm) wave(e.g. 60 GHz) band.

The communication unit 310 transmits and receives a signal, as describedabove. Accordingly, the entirety or a part of the communication unit 310may be called “a transmission unit”, “a reception unit”, or “atransceiver unit”. Also, in the following description, transmission andreception through a wireless channel may be understood to include theaforementioned processing of the communication unit 310.

The storage unit 320 stores data such as a basic program, an applicationprogram, and configuration information for the operation of theterminal. The storage unit 320 may be configured as a volatile memory, anon-volatile memory, or a combination of a volatile memory and anon-volatile memory. The storage unit 320 provides stored data inresponse to a request of the control unit 330.

The control unit 330 controls overall operations of the terminal. Forexample, the control unit 330 transmits and receives a signal throughthe communication unit 310. Further, the control unit 330 records andreads data in and from the storage unit 320. In addition, the controlunit 330 may perform functions of a protocol stack required in acommunication protocol. To this end, the control unit 330 may include atleast one processor or microprocessor, or may be a part of a processor.Also, the control unit 330 and apart of the communication unit 310 maybe called a communication processor (CP).

According to various embodiments, if the terminal 120 configures asidelink unicast session with another terminal, the control unit 330 mayperform a procedure of determining whether the terminal 120 is locatedin the coverage of the base station and then obtaining an RLCtransmission mode and RLC configuration information of the sidelinkunicast session from the base station and a procedure of determiningthat the terminal 120 is not located in the coverage of the base stationand then obtaining pre-configured RLC transmission mode and RLCconfiguration information according to a V2X service profile. Forexample, the control unit 330 may control the terminal to performoperations according to various embodiments described later.

FIGS. 4A to 4C illustrates a configuration of a communication unit in awireless communication system according to various embodiments. FIGS. 4Ato 4C illustrate examples of a specific configuration of the wirelesscommunication unit 210 in FIG. 2 or the communication unit 310 in FIG.3. Specifically, FIGS. 4A to 4C illustrate elements performingbeamforming, which are a part of the wireless communication unit 210 inFIG. 2 or the communication unit 310 in FIG. 3.

Referring to FIG. 4A, the wireless communication unit 210 or thecommunication unit 310 includes an encoding and modulating unit 402, adigital beamforming unit 404, a plurality of transmission paths 406-1 to406-N, and an analog beamforming unit 408.

The encoding and modulating unit 402 performs channel encoding. Forchannel encoding, at least one of a low density parity check (LDPC)code, a convolution code, and a polar code may be used. The encoding andmodulating unit 402 generates modulation symbols by performingconstellation mapping.

The digital beamforming unit 404 performs beamforming on a digitalsignal (e.g. modulation symbols). To this end, the digital beamformingunit 404 multiplies beamforming weights to the modulation symbols. Thebeamforming weights are used for changing the size and the phase of asignal, and may be called “a precoding matrix”, “a precoder”, etc. Thedigital beamforming unit 404 outputs, to the plurality of transmissionpaths 406-1 to 406-N, the modulation symbols, which have been subjectedto digital beamforming. According to a multiple input multiple output(MIMO) transmission scheme, the modulation symbols may be multiplexed,or the same modulation symbols may be provided to the plurality oftransmission paths 406-1 to 406-N.

The plurality of transmission paths 406-1 to 406-N convert, into analogsignals, digital signals having been subjected to digital beamforming.To this end, each of the plurality of transmission paths 406-1 to 406-Nmay include an inverse fast Fourier transform (IFFT) calculation unit, acyclic prefix (CP) insertion unit, a DAC, and an up-conversion unit. TheCP insertion unit is designed for an orthogonal frequency divisionmultiplexing (OFDM) scheme, and may be excluded in another physicallayer scheme (e.g. filter bank multi-carrier (FBMC)). That is, theplurality of transmission paths 406-1 to 406-N provide independentsignal processing processes for multiple streams generated throughdigital beamforming, respectively. However, according to animplementation method, a part of the elements of the plurality oftransmission paths 406-1 to 406-N may be shared.

The analog beamforming unit 408 performs beamforming on an analogsignal. To this end, the digital beamforming unit 404 multipliesbeamforming weights to analog signals. The beamforming weights are usedfor changing the size and the phase of a signal. Specifically, accordingto a connection structure between the plurality of transmission paths406-1 to 406-N and antennas, the analog beamforming unit 408 may beconfigured as illustrated in FIG. 4B or FIG. 4C.

Referring to FIG. 4B, signals input to the analog beamforming unit 408undergo phase/size conversion and an operation of amplification, and arethen transmitted through antennas. The signals in the paths aretransmitted through different antenna sets, that is, antenna arrays. Inrelation to processing of a signal input through a first path, thesignal is converted into a signal stream including signals having anidentical phase or size or different phases or sizes by phase/sizeconversion units 412-1-1 to 412-1-M, the converted signals included inthe signal stream are amplified by amplifiers 414-1-1 to 414-1-M, andthen the amplified signals are transmitted through antennas,respectively.

Referring to FIG. 4C, signals input to the analog beamforming unit 408undergo phase/size conversion and an operation of amplification, and arethen transmitted through antennas. The signals in the paths aretransmitted through an identical antenna set, that is, an antenna array.In relation to processing of a signal input through a first path, thesignal is converted into a signal stream including signals having anidentical phase or size or different phases or sizes by phase/sizeconversion units 412-1-1 to 412-1-M, and the converted signals includedin the signal stream are amplified by amplifiers 414-1-1 to 414-1-M. Inorder to be transmitted through a single antenna array, amplifiedsignals are added together based on antenna elements by adding units416-1-1 to 416-1-M, and then the added signals are transmitted throughthe antennas, respectively.

FIG. 4B illustrates an example of using independent antenna arrays fortransmission paths, and FIG. 4C illustrates an example of sharing asingle antenna array between transmission paths. However, according toanother embodiment, some transmission paths may use independent antennaarrays, and the remaining transmission paths may share a single antennaarray. Further, according to yet another embodiment, a switchablestructure between transmission paths and antenna arrays may be appliedthereby allowing use of a structure which is changeable adaptivelyaccording to a situation.

A V2X service may be divided into a basic safety service and an advancedservice. The basic safety service may correspond to detailed servicesincluding a vehicle notification (CAM or BSM) service, a left-turnnotification service, a proceeding vehicle collision warning service, anemergency vehicle approach notification service, a front obstaclewarning service, an intersection signal information service, and thelike. Further, the basic safety service is designed to transmit orreceive V2X information by using a broadcast transmission scheme and maysupport the transmission or reception by using a conventional 4G-basedV2X communication scheme. The advanced service not only needs tightenedQoS requirements more than those of the basic safety service, but alsorequires a method of transmitting or receiving V2X information by usingunicast and groupcast transmission schemes allowing transmission orreception of V2X information in a particular vehicle group or betweentwo vehicles. The advanced service may correspond to detailed servicesincluding a group driving service, a self-driving service, a remotedriving service, an extended sensor-based V2X service, and the like. Inthe disclosure, a method for supporting, for a vehicle-to-vehicle directcommunication, a unicast communication scheme required for an advancedservice will be described according to various embodiments. In thedisclosure, a vehicle-to-vehicle direct communication scheme whichdifferentiates between a basic safety service and an advanced servicewill be described according to various embodiments.

FIG. 5 illustrates direct communication between terminals by a unicastscheme according to various embodiments.

FIG. 5 illustrates four scenarios to which embodiments can be applied.

(5-1) The terminals 120 and 130 located in the coverage of the basestation 110 may perform unicast type direct communication. According toan embodiment, the base station 110 may manage sidelink resourceinformation and configuration information of a transmission mode (RLC AMmode or RLC UM mode) of a radio link control (RLC) layer, the pieces ofinformation being used to perform a unicast type direct communication bythe terminals 120 and 130.

(5-2) The terminal 120 located in the coverage of the base station 110and the terminal 130 not located in the base station coverage mayperform unicast type direct communication. According to an embodiment,the base station 110 may manage sidelink resource information andconfiguration information of an RLC layer transmission mode, the piecesof information being used to perform a unicast type direct communicationby the terminals 120 and 130.

(5-3) The terminals 120 and 130 which are not located in the coverage ofthe base station 110 may perform unicast type direct communication.According to an embodiment, the terminals 120 and 130 may obtain apre-configured sidelink resource used to perform a unicast type directcommunication, determine an RLC layer transmission mode, and obtainpre-configured RLC configuration information corresponding to thedetermined RLC layer transmission mode.

(5-4) The terminal 120 located in the coverage of the base station 110and a terminal 160 located in the coverage of a base station 150 mayperform unicast type direct communication. According to an embodiment,the base stations 110 and 150 may manage and exchange sidelink resourceinformation and configuration information of an RLC layer transmissionmode, the pieces of information being used to perform a unicast typedirect communication by the terminals 120 and 160, and may transfer thepieces of information to the corresponding terminal located in thecoverage of each of the base stations 110 and 150.

Detailed operations for scenarios (5-1), (5-2), (5-3), and (5-4) may beperformed as described below.

A transmission terminal may obtain sidelink resource information andconfiguration information of an RLC layer transmission mode, which areused to perform a unicast type direct communication by the transmissionterminal, through at least one route among a route of obtaining thepieces of information from a base station and a route of obtaining thepieces of information from pre-configured information. The configurationinformation may include at least one of transmission-specificinformation (information used for transmission) and information whichshould be shared by the transmission terminal and a correspondingreception terminal. A reception terminal may obtain sidelink resourceinformation and configuration information of an RLC layer transmissionmode, which are used to perform a unicast type direct communication bythe reception terminal, through at least one route among a route ofobtaining the pieces of information from a base station, a route ofobtaining the pieces of information from pre-configured information, anda route of randomly configuring the pieces of information by theterminal. The configuration information may include reception-specificinformation. The operations may be applied to a transmission terminaland a reception terminal located in the coverage of a base station and atransmission terminal and a reception terminal not located in thecoverage of a base station.

Detailed operations for scenarios (5-1) may include the followingoperations.

The terminal 120 or 130 may obtain, from the base station 110, sidelinkresource information and configuration information of an RLC layertransmission mode, which are used for performing a unicast type directcommunication. If the terminal 120 or 130 is a transmission terminal ofa direct unicast communication, the terminal 120 or 130 may obtain, fromthe base station 110, the sidelink resource information andconfiguration information according to the RLC layer transmission mode.If the terminal 120 or 130 is a reception terminal of a direct unicastcommunication, the terminal 120 or 130 may obtain, from the base station110, at least one of ARQ feedback configuration information andreception-specific configuration information according to the RLC layertransmission mode of the sidelink direct communication. If the terminal120 or 130 is a reception terminal of a direct unicast communication,the terminal 120 or 130 may randomly configure at least one of ARQfeedback configuration information and reception-specific configurationinformation according to the RLC layer transmission mode of the sidelinkdirect communication. If the terminal 120 or 130 is a reception terminalof a direct unicast communication, the terminal 120 or 130 may obtainpre-configured reception-specific configuration information according toan RLC layer transmission mode, which is used for performing unicasttype direct communication.

Detailed operations for scenarios (5-2) may include the followingoperations.

The terminal 120 may obtain, from the base station 110, sidelinkresource information and configuration information of an RLC layertransmission mode, which are used for performing a unicast type directcommunication. The terminal 130 may obtain pre-configured sidelinkresource information and pre-configured configuration information of anRLC layer transmission mode, which are used for performing a unicasttype direct communication. If the terminal 120 is a transmissionterminal of a direct unicast communication, the terminal 120 may obtain,from the base station 110, sidelink resource information andconfiguration information of an RLC layer transmission mode, which areused for performing unicast type direct communication. If the terminal130 is a reception terminal of a direct unicast communication, theterminal 130 may obtain pre-configured reception-specific configurationinformation according to an RLC layer transmission mode, which is usedfor performing unicast type direct communication. If the terminal 130 isa reception terminal of a direct unicast communication, the terminal 130may randomly configure reception-specific configuration informationaccording to an RLC layer transmission mode, which is used forperforming unicast type direct communication.

If the terminal 120 is a reception terminal of a direct unicastcommunication, the terminal 120 may obtain, from the base station 110,reception-specific configuration information according to an RLC layertransmission mode, which is used for performing unicast type directcommunication. If the terminal 120 is a reception terminal of a directunicast communication, the terminal 120 may obtain pre-configuredreception-specific configuration information according to an RLC layertransmission mode, which is used for performing unicast type directcommunication. If the terminal 120 is a reception terminal of a directunicast communication, the terminal 120 may randomly configurereception-specific configuration information according to an RLC layertransmission mode, which is used for performing unicast type directcommunication. If the terminal 130 is a transmission terminal of adirect unicast communication, the terminal 130 may obtain pre-configuredconfiguration information according to an RLC layer transmission mode,which is used for performing unicast type direct communication.

Detailed operations for scenarios (5-3) may include the followingoperations.

If the terminal 120 or 130 is a transmission terminal of a directunicast communication, the terminal 120 or 130 may obtain pre-configuredconfiguration information according to an RLC layer transmission mode,which is used for performing unicast type direct communication. If theterminal 120 or 130 is a reception terminal of a direct unicastcommunication, the terminal 120 or 130 may obtain pre-configuredreception-specific configuration information according to an RLC layertransmission mode, which is used for performing unicast type directcommunication. If the terminal 120 or 130 is a reception terminal of adirect unicast communication, the terminal 120 or 130 may randomlyconfigure reception-specific configuration information according to anRLC layer transmission mode, which is used for performing unicast typedirect communication.

Detailed operations for scenarios (5-4) may include the followingoperations.

The terminal 120 may obtain, from the base station 110, sidelinkresource information and configuration information of an RLC layertransmission mode, which are used for performing a unicast type directcommunication. The terminal 160 may obtain, from the base station 150,sidelink resource information and configuration information of an RLClayer transmission mode, which are used for performing a unicast typedirect communication.

If the terminal 120 is a transmission terminal of a direct unicastcommunication, the terminal 120 may obtain, from the base station 110,sidelink resource information and configuration information of an RLClayer transmission mode, which are used for performing unicast typedirect communication. If the terminal 160 is a reception terminal of adirect unicast communication, the terminal 160 may obtain, from the basestation 150, reception-specific configuration information according toan RLC layer transmission mode, which are used for performing unicasttype direct communication. If the terminal 160 is a reception terminalof a direct unicast communication, the terminal 160 may obtainpre-configured reception-specific configuration information according toan RLC layer transmission mode, which is used for performing unicasttype direct communication. If the terminal 160 is a reception terminalof a direct unicast communication, the terminal 160 may randomlyconfigure reception-specific configuration information according to anRLC layer transmission mode, which is used for performing unicast typedirect communication.

If the terminal 160 is a transmission terminal of a direct unicastcommunication, the terminal 160 may obtain, from the base station 150,sidelink resource information and configuration information of an RLClayer transmission mode, which are used for performing unicast typedirect communication. If the terminal 120 is a reception terminal of adirect unicast communication, the terminal 120 may obtain, from the basestation 110, reception-specific configuration information according toan RLC layer transmission mode, which are used for performing unicasttype direct communication. If the terminal 120 is a reception terminalof a direct unicast communication, the terminal 120 may obtainpre-configured reception-specific configuration information according toan RLC layer transmission mode, which is used for performing unicasttype direct communication. If the terminal 120 is a reception terminalof a direct unicast communication, the terminal 120 may randomlyconfigure reception-specific configuration information according to anRLC layer transmission mode, which is used for performing unicast typedirect communication.

FIG. 6 illustrates configuring a session for unicast transmissionbetween terminals according to various embodiments.

Referring to FIG. 6, (1) the terminal 120 may perform a V2X serviceregistration procedure with a V2X server or a V2X control center. (2)The terminal 130 may perform a V2X service registration procedure withthe V2X server or the V2X control center. (3) The terminals 120 and 130may perform a unicast session establishment procedure to receive anidentical V2X service in a unicast scheme. The unicast sessionestablishment procedure indicated by the number (3) may include a 2-waytransaction of transmitting a unicast session request message by theterminal 120, as indicated by the number (3-1), and transmitting aunicast session response message in response to the unicast sessionrequest message by the terminal 130, as indicated by the number (3-2),or may include a 3-way transaction of transmitting a unicast sessionconfirm message in response to the unicast session response message bythe terminal 120. The above description is made under the assumptionthat the terminal 120 transmits the unicast session request message, buteither of the terminals 120 and 130 can transmit a unicast sessionrequest message. In a case of a group driving service, a terminal of aleader vehicle during corresponding group driving may transmit a unicastsession request message and a terminal of a following vehicle maytransmit a unicast session response message, so that a unicast sessionis established. In another embodiment, a terminal of a following vehicleduring corresponding group driving may transmit a unicast sessionrequest message and a terminal of a leader vehicle may transmit aunicast session response message, so that a unicast session isestablished. Detailed description for various embodiments of a unicastsession establishment procedure for the other V2X services will beomitted in the disclosure.

According to an embodiment, the terminals 120 and 130 may perform aprocedure for configuring an RLC transmission mode during the unicastsession establishment procedure indicated by the number (3).

According to another embodiment, the terminals 120 and 130 may perform aprocedure for configuring an RLC transmission mode after the unicastsession establishment procedure indicated by the number (3).

Session information obtained by the terminals 120 and 130 through theunicast session establishment indicated by the number (3) may include atleast one of the following contents.

-   -   Session identifier (session ID), transmission type (unicast,        broadcast, and groupcast information), destination identifier        (DST ID), and source identifier (SRC ID)    -   A session identifier may indicate a unicast session identifier        established between the two terminals. If the two terminals        perform a unicast transmission, the terminals obtain an        identical session identifier.    -   A transmission type may indicate one of unicast, groupcast, and        broadcast.    -   A destination identifier may indicate a destination identifier        of a V2X service to be serviced through the unicast session        established between the two terminals. If the two terminals        perform a unicast transmission, the terminals obtain an        identical destination identifier.    -   A source identifier may indicate a source identifier of a V2X        service to be serviced through the unicast session established        between the two terminals. If the two terminals perform a        unicast transmission, the terminals obtain an identical source        identifier.    -   If the session identifier, the destination identifier, or the        source identifier includes transmission type information, the        above described transmission type information may be omitted.    -   Base station identifier: if it is determined that each of the        two terminals is located in a base station coverage, each of the        two terminals may provide the opposite terminal with identifier        information of its own serving base station. The base station        identifier may include at least one of a base station ID, a cell        ID, cell frequency band information, and bandwidth part (BWP)        information.    -   TX profile: a sidelink transmission profile which the two        terminals are to apply to the unicast session (a TX profile may        include sidelink protocol version information, a RAT        configuration index of a sidelink protocol, or the like. The        sidelink protocol version information may indicate a 3GPP        sidelink version number such as rel-14, rel-15, rel-16, . . . ;        LTE-V2X, LTE-eV2X, NR-V2X, . . . ; V2X Phase 1, V2X phase 2, V2X        phase 3, . . . ; or Rel-14 compatible, Rel-14 non-compatible,        Rel-15 non-compatible, Rel-16 compatible. The RAT configuration        index of a sidelink protocol may indicate information indicating        a radio profile (MCS, TX parameter, RX parameter, etc.) of a        sidelink.)

FIGS. 7A to 7F illustrate a terminal-to-base station signaling procedurefor configuring an RLC transmission mode for unicast transmissionbetween terminals according to various embodiments.

FIGS. 7A to 7F illustrate embodiments for configuring an RLCtransmission mode for unicast transmission according to four scenariosillustrated in FIG. 5.

FIG. 7A illustrates an embodiment in which if a terminal is in anRRC-connected state, the terminal obtains RLC configuration informationfor sidelink unicast transmission from a base station. To achieve theabove purpose, (1) the terminal may transmit a UE assistance informationmessage to the base station. The UE assistance information message mayinclude at least one of unicast session information (identifier),transmission type information (unicast, groupcast, and broadcast),service QoS information, and preferred RLC mode information of theterminal. (2) The base station may configure an RLC transmission modeand RLC configuration which the terminal is to apply to a sidelinkunicast transmission, on the basis of the information included in the UEassistance information message. (3) The base station may transmit, tothe terminal, an RRC configuration message including the RLCtransmission mode and RLC configuration information for unicastsidelink, which are determined in the operation indicated by the number(2).

An operation of determining an RLC transmission mode and configurationrequired for unicast sidelink by the base station in the operationindicated by the number (2) is performed as follow.

1. An RLC AM mode determination condition may include at least one ofthe following embodiments.

(1) A session identifier or transmission type information indicates aterminal-to-terminal unicast transmission.

(2) Service QoS information (data rate, reliability, latency,communication range, and priority) indicates a terminal-to-terminalunicast transmission.

(3) Service QoS information (data rate, reliability, latency,communication range, and priority) indicates a particular data rate, aparticular reliability, a particular latency time, a particularcommunication range, or a particular priority.

(In an embodiment, the base station may manage a reference value of aparticular data rate, a particular reliability, a particular latencytime, a particular communication range, or a particular priority, inwhich RLC AM mode should be operated. In another embodiment, a referencevalue of a particular data rate, a particular reliability, a particularlatency time, a particular communication range, or a particular priorityin which RLC AM mode should be operated may be pre-configured.)

(4) A service identifier, an application identifier, a destinationidentifier, or a source identifier indicates a terminal-to-terminalunicast transmission.

(5) A service identifier, an application identifier, a destinationidentifier, or a source identifier indicates RLC AM mode.

(In an embodiment, the base station may manage information relating to aparticular service, a particular application, a particular destination,or a particular source in which RLC AM mode should be operated. Inanother embodiment, information relating to a particular service, aparticular application, a particular destination, or a particular sourcein which RLC AM mode should be operated may be pre-configured.

(6) Preferred RLC mode information of the terminal indicates RLC AMmode.

2. An embodiment of determining an RLC transmission mode of the terminalby the base station may include at least one of the following contents.

In an embodiment, UE assistance information may include sessioninformation (identifier) and transmission type information which areobtained in unicast session establishment. The base station maydetermine RLC AM mode or RLC UM mode from a corresponding sessionidentifier and the transmission type information. For example, if it isdetermined that the session identifier and the transmission typeinformation require terminal-to-terminal unicast transmission based onRLC AM, the base station may configure RLC AM mode.

In another embodiment, UE assistance information may include a sessionidentifier, transmission type information, and service QoS information(data rate, reliability, latency, communication range, priority, etc.)which are obtained in unicast session establishment. The base stationmay determine RLC AM mode or RLC UM mode, based on the sessionidentifier, transmission type information, and service QoS information.For example, if it is determined that the session identifier,transmission type information, and service QoS information requireterminal-to-terminal unicast transmission based on RLC AM the basestation may configure RLC AM mode.

In another embodiment, UE assistance information may include at leastone of a session identifier, transmission type information, service QoSinformation (data rate, reliability, latency, communication range,priority, etc.), a service identifier, an application identifier, adestination identifier, and a source identifier which are obtained inunicast session establishment. The base station may determine RLC AMmode or RLC UM mode, based on the at least one of a session identifier,transmission type information, service QoS information, a serviceidentifier, an application identifier, a destination identifier, and asource identifier. For example, if it is determined that the serviceidentifier requires terminal-to-terminal unicast transmission based onRLC AM, the base station may configure RLC AM mode. For another example,if it is determined that the destination identifier requiresterminal-to-terminal unicast transmission based on RLC AM, the basestation may configure RLC AM mode.

In another embodiment, UE assistance information may include at leastone of a session identifier, transmission type information, service QoSinformation (data rate, reliability, latency, communication range,priority, etc.), a service identifier, an application identifier, adestination identifier, a source identifier, and preferred RLC modeinformation of the terminal, which are obtained in unicast sessionestablishment. The base station may configure RLC AM mode or RLC UMmode, based on the information.

FIG. 7B illustrates an embodiment in which, if it is determined thateach of the terminals 120 and 130 having obtained unicast sessioninformation according to the embodiment illustrated in FIG. 6 is locatedin a base station coverage, obtaining RLC transmission modeconfiguration information for unicast session from a base station.

(1) The terminal 120 may transmit a UE assistance information message toa base station. The UE assistance information message may include a basestation identifier, RLC transmission mode assistance information, andunicast session information, for example, at least one information amonga session identifier, a destination identifier, a source identifier, anda transmission type. According to an embodiment, a base stationidentifier may correspond to at least one of a base station ID, a cellID, cell frequency band information, and bandwidth part (BWP)information. (2) The terminal 130 may transmit a UE assistanceinformation message to the base station. The UE assistance informationmessage may include a base station identifier, RLC transmission modeassistance information, and unicast session information, for example, atleast one information among a session identifier, a destinationidentifier, a source identifier, and a transmission type. (3) If thebase station receives a UE assistance information message includingsession information or RLC transmission mode assistance information fromthe terminals 120 and 130 and the message includes a base stationidentifier, the base station may determine that RLC informationconfiguration for unicast transmission with a terminal located in thecoverage of an adjacent base station is required. If the UE assistanceinformation message does not include a base station identifier, the basestation may determine that RLC information configuration for unicasttransmission with a terminal located in the coverage of the same basestation is required.

The base station may determine, through session information, that is, anidentical session identifier, an identical destination identifier, anidentical source identifier, and a transmission type, that the twoterminals are to perform a sidelink unicast transmission. The basestation may determine an RLC transmission mode for sidelink unicast ofthe terminals 120 and 130. The base station may select one of RLC AMmode (acknowledge mode) or RLC UM mode (unacknowledged mode) as an RLCtransmission mode. The base station may configure sidelink RLCconfiguration information according to a selected RLC transmission mode.

If the base station selects RLC AM mode, RLC config indicating RLCconfiguration information may be configured as below while includingsidelink RLC configuration of TX and RX.

An embodiment of RLC configuration information for sidelink is asfollows.

SL RLC-BearerConfig ::= SEQUENCE { logicalChannelIdentityLogicalChannelIdentity servedRadioBearer SLRB-Identity SL_rlc-ConfigSL_RLC-Config mac-LogicalChannelConfig LogicalChannelConfig }SL_RLC-Config ::= CHOICE { am SL-AM-RLC, um SL-UM-RLC } SL-AM-RLC ::=SEQUENCE { //TX and RX sn-FieldLength SN-FieldLengthAM, t-PollRetransmitT-PollRetransmit, pollPDU PollPDU pollByte PollByte, maxRetxThresholdENUMERATED { t1, t2, t3, t4, t6, t8, t16, t32 }, t-ReassemblyT-Reassembly, t-StatusProhibit T-StatusProhibit } T-PollRetransmit ::=ENUMERATED { ms5, ms10, ms15, ms20, ms25, ms30, ms35, ms40, ms45, ms50,ms55, ms60, ms65, ms70, ms75, ms80, ms85, ms90, ms95, ms100, ms105,ms110, ms115, ms120, ms125, ms130, ms135, ms140, ms145, ms150, ms155,ms160, ms165, ms170, ms175, ms180, ms185, ms190, ms195, ms200, ms205,ms210, ms215, ms220, ms225, ms230, ms235, ms240, ms245, ms250, ms300,ms350, ms400, ms450, ms500, ms800, ms1000, ms2000, ms4000, spare5,spare4, spare3, spare2, spare1} PollPDU ::= ENUMERATED { p4, p8, p16,p32, p64, p128, p256, p512, p1024, p2048 p4096, p6144, p8162, p12288,p16384 p20480, p24576, p28672, p32768, p40960, p49152, p57344, p65536,infinity, spare8, spare7, spare6 spare5, spare4, spare3, spare2, spare1}PollByte ::= ENUMERATED { kB1, kB2, kB5, kB8, kB10, kB15, kB25, kB50,kB75, kB100, kB125, kB250, kB375, kB500, kB750, kB1000, kB1250, kB1500,kB2000, kB3000, kB4000, kB4500, kB5000, kB5500, kB6000, kB6500, kB7000,kB7500, mB8, mB9, mB10, mB11, mB12, mB13, mB14, mB15, mB16, mB17, mB18,mB20, mB25, mB30, mB40, infinity, spare20, spare19, spare18, spare17,spare16, spare15, spare14, spare13, spare12, spare11, spare10, spare9,spare8, spare7, spare6, spare5, spare4, spare3, spare2, spare1}T-Reassembly ::= ENUMERATED { ms0, ms5, ms10, ms15, ms20, ms25, ms30,ms35, ms40, ms45, ms50, ms55, ms60, ms65, ms70, ms75, ms80, ms85, ms90,ms95, ms100, ms110, ms120, ms130, ms140, ms150, ms160, ms170, ms180,ms190, ms200, spare1} T-StatusProhibit ::= ENUMERATED { ms0, ms5, ms10,ms15, ms20, ms25, ms30, ms35, ms40, ms45, ms50, ms55, ms60, ms65, ms70,ms75, ms80, ms85, ms90, ms95, ms100, ms105, ms110, ms115, ms120, ms125,ms130, ms135, ms140, ms145, ms150, ms155, ms160, ms165, ms170, ms175,ms180, ms185, ms190, ms195, ms200, ms205, ms210, ms215, ms220, ms225,ms230, ms235, ms240, ms245, ms250, ms300, ms350, ms400, ms450, ms500,ms800, ms1000, ms1200, ms1600, ms2000, ms2400, spare2, spare1}Sn-FieldLengthAM ::= ENUMERATED {size12, size18}

If the base station selects RLC UM mode, an embodiment of RLCconfiguration information is as follows.

SL RLC-BearerConfig ::= SEQUENCE { logicalChannelIdentityLogicalChannelIdentity, servedRadioBearer SLRB-Identity SL_rlc-ConfigSL_RLC-Config mac-LogicalChannelConfig LogicalChannelConfig }SL_RLC-Config ::= CHOICE { am SL-AM-RLC um SL-UM-RLC }

In another embodiment, if the base station selects RLC UM mode, the basestation may transmit, to the terminals 120 and 130, an RRC configurationmessage in which separate RLC configuration information is notconfigured. The case described above can be applied if the system isdesigned such that sidelink RLC UM configuration information has alreadybeen configured for the terminals 120 and 130. If the base stationselects RLC UM mode, the base station may transmit packettransmission/reception resource information for RLC UM.

The base station may transmit an RRC configuration message including thesidelink RLC configuration information to the terminal 120 in responseto the UE assistance information message. (4) The base station maytransmit an RRC configuration message including the sidelink RLCconfiguration information to the terminal 130 in response to the UEassistance information message.

In another embodiment, an RRC configuration message transmitted by thebase station to the terminals 120 and 130 may include transmissionresource information for sidelink RLC AM mode.

The base station may provide sidelink resources for data packettransmission and sidelink resources for ARQ feedback transmission. Mode1 indicates that the base station schedules sidelink resources. Mode 2indicates that the terminal selects sidelink resources. In the case ofmode 1, sidelink resources for data packet transmission may be allocatedin a semi persistence scheduling (SPS) scheme or a configured grant typescheme. In the case of mode 1, sidelink resources for ARQ feedbacktransmission may be allocated in a SPS scheme or a configured grant typescheme.

The following description relates to an embodiment of transmissionresource information of sidelink RLC AM mode.

-   -   Allocate resources for transmitting a data packet in a mode 1        and SPS scheme    -   Allocate ARQ feedback transmission resources in a mode 1 and SPS        scheme

(The SPS period of the ARQ feedback resources may be determined to bethe same as or similar to the period of an ARQ feedback poll.)

The following description relates to another embodiment of transmissionresource information of sidelink RLC AM mode.

-   -   Allocate resources for transmitting a data packet in a mode 1        and SPS scheme    -   Allocate ARQ feedback transmission resources in a mode 1 and SPS        scheme

(The SPS period of the ARQ feedback resources may be determined to bethe same as or similar to the period of an ARQ feedback poll.)

-   -   If a reception node should transmit ARQ feedback by itself,        instruct the reception node to execute a sidelink buffer status        report (SL BSR)

The following description relates to another embodiment of transmissionresource information of sidelink RLC AM mode.

-   -   Allocate resources for transmitting a data packet in a mode 1        and SPS scheme    -   Allocate ARQ feedback transmission resources in a mode 1 and SPS        scheme

(The SPS period of the ARQ feedback resources may be determined to bethe same as or similar to the period of an ARQ feedback poll.)

-   -   If a reception node should transmit ARQ feedback by itself,        allocate resources in a mode 2 scheme

The following description relates to another embodiment of transmissionresource information of sidelink RLC AM mode.

-   -   Allocate resources for transmitting a data packet in a mode 1        and SPS scheme    -   Allocate (obtain based on sensing) ARQ feedback transmission        resources in a mode 2 scheme (even if a reception node should        transmit ARQ feedback by itself)

The following description relates to another embodiment of transmissionresource information of sidelink RLC AM mode.

-   -   Allocate resources for transmitting a data packet in a mode 2        scheme    -   Allocate ARQ feedback transmission resources in a mode 2 scheme        (even if a reception node should transmit ARQ feedback by        itself)

In another embodiment relating to transmission resource information ofsidelink RLC AM mode, a dynamic resource allocation scheme which employsa mode 1 scheme but is based on a SL BSR may be operated.

FIG. 7C illustrates an embodiment of obtaining RLC transmission modeconfiguration information for a unicast session if it is determined thatthe terminal 120 having obtained unicast session information accordingto the embodiment illustrated in FIG. 6 is located in the coverage of abase station and the terminal 130 is not located in the coverage of abase station. An embodiment indicated by the number (7-3) is made underan assumption that it is determined that the terminal 120 is located inthe coverage of a base station and the terminal 130 is not located inthe coverage of a base station. The terminals 120 and 130 may exchangeinformation relating to whether they are in a base station coverage,during a unicast session configuration procedure. If a terminal islocated in the coverage of a base station, the terminal may transferbase station identifier information. Base station identifier informationmay include at least one of a base station ID, a cell ID, cell frequencyband information, and BWP information. According to the embodimentindicated by the number (7-3), the terminal 120 may determine that theterminal 130 is not located in a base station coverage. In anembodiment, the terminal 120 may transfer, to the base station andthrough a UE assistance information message, instruction informationrequesting RLC configuration information for a unicast session with theterminal 130 which is not located in a base station coverage. In anotherembodiment, the base station may manage a timer for processing an RLCconfiguration information request for an identical unicast session. Ifthe base station which has received a UE assistance information messagerequesting RLC configuration information for a unicast session from theterminal 120 starts the timer and fails to receive a message requestingRLC configuration information for the same unicast session from theterminal 130 until the timer is expired, the base station may recognizethat the terminal 130 is not located in a base station coverage. Themessage requesting RLC configuration information for the same unicastsession from the terminal 130 may correspond to a UE assistanceinformation message which is received directly from the terminal 130, ora message which is received from an adjacent base station, which is aserving base station of the terminal 130.

(1) The terminal 120 may transmit a UE assistance information message tothe base station. The UE assistance information message may include abase station identifier, RLC transmission mode assistance information,an out-of-coverage indicator, and unicast session information, forexample, at least one information among a session identifier, adestination identifier, a source identifier, and a transmission type.According to an embodiment, the base station identifier may correspondto at least one of a base station ID, a cell ID, cell frequency bandinformation, and bandwidth part (BWP) information. The out-of-coverageindicator corresponds to information indicating that the terminal 130having configured a unicast session with the terminal 120 fails to be ina base station coverage. (2) If the base station receives UE assistanceinformation messages including RLC transmission mode assistanceinformation or unicast session information of the terminals 120 and 130and the messages include a base station identifier, the base station maydetermine that RLC information configuration for unicast transmissionwith a terminal located in the coverage of an adjacent base station isrequired. If the UE assistance information messages do not include abase station identifier, the base station may determine that RLCinformation configuration for unicast transmission with a terminallocated in the coverage of the same base station is required. If themessages include an out-of-coverage indicator, the base station maydetermine that a unicast session with a terminal which is not located ina base station coverage has been configured. The base station maydetermine a sidelink unicast RLC transmission mode for the terminals 120and 130. The base station may select one of RLC AM mode (acknowledgemode) or RLC UM mode (unacknowledged mode) as an RLC transmission mode.The base station may configure sidelink RLC configuration informationaccording to a selected RLC transmission mode. Sidelink RLCconfiguration information of the case of selecting RLC AM mode orsidelink RLC configuration information of the case of selecting RLC UMmode has been already described above in section (7-2). The base stationmay transmit the sidelink RLC configuration information for each RLCtransmission mode to the terminal 120. The base station may providesidelink resources for data packet transmission and sidelink resourcesfor ARQ feedback transmission. (3) The terminal 120 may receive sidelinkRLC configuration information from the base station and transfer theobtained information to the terminal 130. (4) The terminal 130 mayobtain sidelink RLC configuration information from the terminal 120. Thesidelink RLC configuration information exchanged between the twoterminals in the operations indicated by the numbers (3) and (4) issidelink RLC configuration information of the operation indicated by thenumber (2), and is configuration information to be applied if an RLCtransmission mode is RLC AM or RLC UM. The information exchanged in theoperations indicated by the numbers (3) and (4) may include allocationinformation relating to sidelink resources for data packet transmissionand sidelink resources for ARQ feedback transmission.

FIG. 7D illustrates an embodiment of configuring an RLC transmissionmode for a unicast session if it is determined that the terminals 120and 130 having obtained unicast session information according to theembodiment illustrated in FIG. 6 are not located in a base stationcoverage.

FIG. 7D illustrates a case in which it is determined that the terminals120 and 130 are not located in a base station coverage. The terminals120 and 130 may exchange information relating to whether the terminals120 and 130 are located in a base station coverage, during a unicastsession configuration procedure. If it is not determined that theterminals 120 and 130 are located in a base station coverage, oneterminal among the two terminals may start a procedure of configuring anRLC transmission mode according to an embodiment. For example, aterminal having started a unicast session procedure may start aprocedure of configuring an RLC transmission mode. In another example, aterminal of a leader vehicle of group driving may start a procedure ofconfiguring an RLC transmission mode. (1) The terminal 120 may obtainRLC configuration information pre-configured to be used in anout-of-coverage situation. The terminal 120 may determine an RLCtransmission mode (RLC AM or RLC UM) according to V2X serviceinformation or session information obtained during a unicast sessionconfiguration procedure and determine RLC configuration according to adetermined transmission mode. For example, according to pre-configuredinformation, if a V2X service to be performed by the two terminals isconfigured to use RLC AM transmission mode, the two terminals may decideto use RLC AM transmission mode and RLC AM configuration information.(2) The terminal 120 may transfer, to the terminal 130, RLCconfiguration information determined in the operation indicated by thenumber (1). (3) The terminal 130 may identify RLC configuration receivedfrom the terminal 120 and then transfer a response message relating tothe determined RLC configuration. The information exchanged in theoperations indicated by the numbers (2) and (3) may include allocationinformation relating to sidelink resources for data packet transmissionand sidelink resources for ARQ feedback transmission.

According to another embodiment, if configuration information which thetwo terminals are to apply to the RLC transmission mode of the unicastsession can be obtained from pre-configuration, the informationexchanged by the two terminals in the operations indicated by thenumbers (2) and (3) may be simple. For example, a specific RLCconfiguration parameter set for each RLC transmission mode may beobtained from pre-configured configuration, and the messages from theoperations indicated by the numbers (2) and (3) may includeconfiguration index information indicating a corresponding parameter setto be used by the two terminals. Allocation information relating tosidelink resources for data packet transmission and sidelink resourcesfor ARQ feedback transmission may be also obtained from pre-configuredconfiguration, and index information indicating which configuration thetwo terminals is to use may be indicated by the pre-configuredconfiguration.

According to another embodiment, the two terminals may start a procedureof configuring an RLC transmission mode independently. In this case, thetwo terminals may obtain pre-configured RLC configuration information inadvance, wherein pre-configured RLC configuration includes definedmapping information indicating which RLC configuration is to beconfigured according to V2X service information or session informationobtained during a unicast session configuration procedure of the twoterminals, or indicating which RLC transmission mode (RLC AM or RLC UM)is to be selected according to the V2X information and sessioninformation, and sidelink RLC configuration information of a selectedRLC transmission mode is obtained through the pre-configured RLCconfiguration. For example, if it is determined in an application layerof a terminal that a group driving service is to be performed, a V2Xprofile for supporting the group driving service may instruct use of RLCAM transmission mode. In addition, the V2X profile may indicate an RLCAM configuration parameter set mapped to RLC AM mode. Allocationinformation relating to sidelink resources for data packet transmissionand sidelink resources for ARQ feedback transmission may be alsoindicated by pre-configured configuration.

FIG. 7E illustrates an embodiment of obtaining RLC transmission modeconfiguration information for a unicast session if it is determined thatthe terminal 120 having obtained unicast session information accordingto the embodiment illustrated in FIG. 6 is located in the coverage of abase station 110 and the terminal 130 is located in the coverage of thebase station 150. FIG. 7E illustrates an embodiment of configuring asidelink unicast session for a V2X service between the two terminalslocated in the coverages of different base stations and obtaining an RLCtransmission mode and RLC configuration information to be used forsidelink unicast. In the embodiment, a terminal may transmit a UEassistance information message requesting configuration of an RLCtransmission mode to a serving base station, the message includinginformation of a base station of an opposite terminal, so as to allowsidelink unicast RLC transmission mode configuration information to beexchanged between the base stations. (1) The terminal 120 may transmit aUE assistance information message to the base station 110. The UEassistance information message may include a base station identifier,RLC transmission mode assistance information, and unicast sessioninformation, for example, at least one information among a sessionidentifier, a destination identifier, a source identifier, and atransmission type. According to an embodiment, the base stationidentifier may correspond to at least one of a base station ID, a cellID, cell frequency band information, and bandwidth part (BWP)information. (2) The terminal 130 may transmit a UE assistanceinformation message to the base station 150. The UE assistanceinformation message may include a base station identifier, RLCtransmission mode assistance information, and unicast sessioninformation, for example, at least one information among a sessionidentifier, a destination identifier, a source identifier, and atransmission type. (3) The base stations 110 and 150 having received UEassistance information messages including session information or RLCtransmission mode assistance information from the terminals 120 and 130may identify opposite base station information from pieces of basestation identifier information included in the UE assistance informationmessages. The base stations 110 and 150 may determine that RLCinformation configuration for sidelink unicast transmission between theterminals 120 and 130 is required, and may determine an RLC transmissionmode and RLC configuration information after consultation with eachother. The base stations 110 and 150 may determine that the twoterminals will perform a sidelink unicast transmission, through sessioninformation, that is, an identical session identifier, an identicaldestination identifier, an identical source identifier, and atransmission type. The base stations 110 and 150 may determine asidelink unicast RLC transmission mode of the terminals 120 and 130. Thebase stations 110 and 150 may configure sidelink RLC configurationinformation for selected RLC transmission modes. The base stations 110and 150 may exchange unicast sidelink transmission resource information(packet transmission resources, ARQ feedback transmission resources,etc.) according to RLC transmission modes. (4) The base station 110 maytransfer, to the terminal 120, an RRC configuration message including anRLC transmission mode and RLC configuration information which isdetermined in the operation indicated by the number (3) and is to beused for sidelink unicast. (5) The base station 150 may transfer, to theterminal 130, an RRC configuration message including an RLC transmissionmode and RLC configuration information which is determined in theoperation indicated by the number (3) and is to be used for sidelinkunicast. The RRC configuration messages from the operations indicated bythe numbers (4) and (5) may also include unicast sidelink transmissionresource information.

FIG. 7F illustrates another embodiment of obtaining RLC transmissionmode configuration information for a unicast session if it is determinedthat the terminal 120 having obtained unicast session informationaccording to the embodiment illustrated in FIG. 6 is located in thecoverage of a base station 110 and the terminal 130 is located in thecoverage of the base station 150. FIG. 7F illustrates an embodiment ofconfiguring a sidelink unicast session for a V2X service between the twoterminals located in the coverages of different base stations andobtaining an RLC transmission mode and RLC configuration information tobe used for sidelink unicast. In the embodiment, each of the terminalsmay transmit a UE assistance information message requestingconfiguration of an RLC transmission mode to its own serving basestation, obtain sidelink unicast RLC transmission mode configurationinformation from the its own serving base station, and then exchange thesidelink unicast RLC transmission mode configuration informationobtained by the terminal itself with the other terminal. (1) Theterminal 120 may transmit a UE assistance information message to thebase station 110. The UE assistance information message may include abase station identifier, RLC transmission mode assistance information,and unicast session information, for example, at least one informationamong a session identifier, a destination identifier, a sourceidentifier, and a transmission type. According to an embodiment, thebase station identifier may correspond to at least one of a base stationID, a cell ID, cell frequency band information, and bandwidth part (BWP)information. (2) The terminal 130 may transmit a UE assistanceinformation message to the base station 150. The UE assistanceinformation message may include a base station identifier, RLCtransmission mode assistance information, and unicast sessioninformation, for example, at least one information among a sessionidentifier, a destination identifier, a source identifier, and atransmission type. (3) The base station 110 may determine a sidelinkunicast RLC transmission mode according to the UE assistance informationmessage of terminal 120 and may transmit an RRC configuration includingconfiguration information according to the RLC transmission mode andtransmission resource information (packet transmission resource, ARQfeedback transmission resource, etc.) according to the RLC transmissionmode. (4) The base station 150 may determine a sidelink unicast RLCtransmission mode according to the UE assistance information message ofterminal 130 and may transmit an RRC configuration includingconfiguration information according to the RLC transmission mode andtransmission resource information (packet transmission resource, ARQfeedback transmission resource, etc.) according to the RLC transmissionmode. (5) The terminals 120 and 130 may exchange an RLC transmissionmode, RLC configuration information, and transmission resourceinformation which are received from the operations indicated by thenumbers (3) and (4) and are to be used for sidelink unicast. Theoperation indicated by the number (5) may be performed when theterminals 120 and 130 should apply the same parameter set according toan RLC transmission mode used for sidelink unicast by the terminals 120and 130, or may be performed for configuring a parameter set requiredfor matching synch (e.g. ARQ feedback poll period) of an RLCtransmission mode operation.

The above description is made according to an example in which aterminal which is to obtain RLC configuration information for sidelinkunicast transmission transmits a UE assistance information message to abase station. However, the message transmitted to obtain the informationby the terminal to the base station may be a random RRC message.

In an embodiment, a UE assistance information message transmitted by theterminal 120 or 130 to the corresponding base station may include anindicator indicating a transmission terminal. In another embodiment, aUE assistance information message transmitted by the terminal 120 or 130to the corresponding base station may include an indicator indicating areception terminal.

In an embodiment, if the terminal 120 or 130 is a transmission terminal,configuration information message obtained from a corresponding basestation may include at least one of sidelink transmission resourceinformation, sidelink RLC configuration information for transmission,and sidelink RLC configuration information which the transmissionterminal and a reception terminal should share. If the terminal 120 or130 is a reception terminal, a configuration information messageobtained from a corresponding base station may include at least one ofsidelink transmission resource information and sidelink RLCconfiguration information for reception.

In an embodiment, a transmission terminal may transmit, to a receptionterminal, at least one of sidelink RLC configuration information whichthe transmission terminal and the reception terminal should share, andsidelink transmission resource information, among pieces ofconfiguration information obtained from a base station.

In an embodiment, a reception terminal may transmit, to a transmissionterminal, at least one of sidelink transmission resource information,sidelink RLC configuration information which the transmission terminaland the reception terminal should share, and ARQ feedback transmissionresource information, among pieces of configuration information obtainedfrom a base station.

In an embodiment, a transmission terminal may transmit, to a receptionterminal, at least one of sidelink RLC configuration information whichthe transmission terminal and the reception terminal should share, andsidelink transmission resource information, among pieces ofpre-allocated configuration information.

In an embodiment, a reception terminal may transmit, to a transmissionterminal, at least one of sidelink RLC configuration information whichthe transmission terminal and the reception terminal should share,sidelink transmission resource information, and ARQ feedbacktransmission resource information, among pieces of pre-allocatedconfiguration information.

In an embodiment, a reception terminal may transmit, to a transmissionterminal, at least one of sidelink RLC configuration information whichthe transmission terminal and the reception terminal should share,sidelink transmission resource information, and ARQ feedbacktransmission resource information, among pieces of random terminalconfiguration information.

FIG. 8 illustrates releasing a session for unicast transmission betweenterminals according to various embodiments.

Referring to FIG. 8, if a V2X service through a unicast session isterminated, the terminals 120 and 130 may perform a unicast sessionrelease procedure. The terminals 120 and 130 may perform an RLCtransmission mode release procedure. (1) In an embodiment, the twoterminals may perform an RLC transmission mode release procedure duringa unicast session release procedure. (1) In another embodiment, the twoterminals may perform a unicast session release procedure after an RLCtransmission mode release procedure.

In the case where the two terminals decide to perform an RLCtransmission mode release procedure, according to an embodiment, if anRLC transmission mode is configured to RLC AM and the terminals 120 and130 are determined to be in a base station coverage, the terminals 120and 130 may transmit an RLC AM configuration release assistance messageto their own serving base stations and perform an RLC transmission moderelease procedure between the two terminals. The RLC AM configurationrelease assistance message may include at least one of a sidelink radiobearer identifier and session information. According to anotherembodiment, if an RLC transmission mode is configured to RLC AM and itis determined that the terminals 120 and 130 are not located in a basestation coverage, only an RLC transmission mode release procedurebetween the two terminals may be performed. According to anotherembodiment, if an RLC transmission mode is configured to RLC AM and itis determined that one terminal among the two terminals is located in abase station coverage, the corresponding terminal may transmit an RLC AMconfiguration release assistance message to its own serving base stationand perform an RLC transmission mode release procedure between the twoterminals. In the above description, an example in which an RLCtransmission mode is configured to RLC AM is explained, but even if RLCUM configuration information is received from a base station, an RLC UMconfiguration release assistance message may be transmitted to theserving base station to release RLC UM configuration information.

(2) After a unicast session release procedure is performed, the terminal120 may perform a V2X service decommissioning procedure through a V2Xserver or a V2X center. (3) After a unicast session release procedure isperformed, the terminal 130 may perform a V2X service decommissioningprocedure through the V2X server or the V2X center.

A detailed method for a case where a terminal located in a base stationcoverage transmits RLC transmission mode release assistanceconfiguration information notifying a corresponding base station ofunicast session release may include at least one of the followingembodiments. RLC transmission mode release assistance configurationinformation may be processed during a hand-over procedure of a terminal.RLC transmission mode release assistance configuration information maybe processed at a time point where it is determined that the terminal isnot located in abase station coverage. RLC transmission mode releaseassistance configuration information may be processed during a processin which the terminal transitions to an RRC_IDLE state or anRRC_INACTIVE state.

FIG. 9 illustrates an operation of a base station for unicasttransmission between terminals according to various embodiments.Referring to FIG. 9, (1) a base station may receive a UE assistanceinformation message from a terminal. The UE assistance informationmessage may include V2X service session information of the terminal. TheV2X service session information may include at least one of sidelinkunicast session information, transmission type information, service QoSinformation, a service identifier, an application identifier, adestination identifier, a source identifier, preferred RLC transmissionmode of the terminal, and a base station identifier according to anembodiment. (2) The base station may determine a sidelink unicast RLCtransmission mode (RLC AM mode or RLC UM mode) on the basis of the V2Xservice session information. As an operation of determining an RLCtransmission mode by the base station, the base station operationsexplained in FIG. 7 may be applied. (3) If a sidelink unicast RLCtransmission mode is determined to RLC AM according to a determinationin the operation indicated by the number (2), the base station mayperform an operation indicated by the number (4) to transmit an RRCconfiguration message including configuration information of thesidelink unicast RLC AM mode to the terminal. The RRC configurationmessage may include information relating to ARQ feedback transmissionresources and packet transmission resources of RLC AM. If a sidelinkunicast RLC transmission mode is determined to RLC UM according to adetermination in the operation indicated by the number (2), the basestation may perform an operation indicated by the number (5) to transmitan RRC configuration message including configuration information of thesidelink unicast RLC UM mode to the terminal. The RRC configurationmessage may include packet transmission resource information of RLC UM.

According to an embodiment, a UE assistance information message which abase station can receive from a terminal may include at least one ofindication information indicating that the terminal is a receptionterminal and indication information indicating that the terminal is atransmission terminal.

According to an embodiment, if the terminal is determined to a receptionterminal, the base station may transfer, to the terminal, at least oneof sidelink transmission resource information, sidelink RLCconfiguration information for reception, and ARQ feedback transmissionresource information.

According to an embodiment, if the terminal is determined to atransmission terminal, the base station may transfer, to the terminal,at least one of sidelink transmission resource information, sidelink RLCconfiguration information for transmission, and sidelink RLCconfiguration information which should be shared by the transmissionterminal and a reception terminal.

FIG. 10 illustrates an operation of a terminal which is in anRRC-connected state, the operation being performed forterminal-to-terminal unicast transmission according to variousembodiments. Referring to FIG. 10, (1) a terminal may transmit a UEassistance information message including V2X service session informationin an operation indicated by the number (2) to request, from a basestation, an RLC transmission mode and configuration information requiredfor sidelink unicast transmission/reception, while the terminal performscommunication in an RRC-connected state with the base station. The V2Xservice session information transmitted to the base station in theoperation indicated by the number (2) may include at least one of asession identifier, transmission type information, service QoSinformation, a service identifier, an application identifier, adestination identifier, a source identifier, preferred RLC transmissionmode of the terminal, and a base station identifier according to anembodiment. (3) If the terminal can receive an RRC configuration messagefrom the base station, the RRC configuration message may include an RLCtransmission mode and RLC configuration information which are to be usedto perform sidelink unicast transmission/reception by the terminal. TheRRC configuration message may include sidelink unicast transmissionresource information according to an RLC transmission mode. (4) Theterminal may determine whether information relating to the RLCtransmission mode received in the operation indicated by the number (3)indicates RLC AM. If RLC AM mode information is included according to adetermination of the operation indicated by the number (4), the terminalmay perform an operation indicated by the number (5) to perform sidelinkunicast transmission/reception by using the RLC AM mode information. Ifthe RLC AM mode information is not included according to a determinationof the operation indicated by the number (4), the terminal may performan operation indicated by the number (6) to perform sidelink unicasttransmission/reception by using RLC UM mode information.

According to an embodiment, a UE assistance information messagetransmitted by a terminal to a base station may include at least one ofindication information indicating that the terminal is a transmissionterminal and indication information indicating that the terminal is areception terminal.

According to an embodiment, a transmission terminal may obtain, throughan RRC configuration message transmitted by a base station, at least oneof sidelink unicast resource information according to an RLCtransmission mode, configuration information for transmission accordingto the RLC transmission mode, and configuration information required tobe shared by the transmission terminal and a reception terminalaccording to the RLC transmission mode.

According to an embodiment, a reception terminal may obtain, through anRRC configuration message transmitted by a base station, at least one ofsidelink unicast resource information according to an RLC transmissionmode, configuration information for reception according to the RLCtransmission mode. ARQ feedback configuration information, and ARQfeedback resource information.

FIG. 11 illustrates an operation of a terminal which is in anRRC-disconnected state, the operation being performed forterminal-to-terminal unicast transmission according to variousembodiments. Referring to FIG. 11, (1) a terminal may require an RLCtransmission mode and configuration information for sidelink unicasttransmission/reception while the terminal performs communication in anRRC-disconnected state (RRC-idle stat or RRC-inactive state) with a basestation. (2) If the terminal receives a V2X service broadcast message(SIB) transmitted by the base station, (3) the terminal may determinewhether the V2X service broadcast message includes RLC configurationinformation for sidelink unicast. The RLC configuration information forsidelink unicast included in the V2X service broadcast message in theoperation indicated by the number (3) may include at least one of RLCtransmission mode mapping information for each V2X service,configuration information of RLC transmission mode AM, and configurationinformation of RLC transmission mode UM according to an embodiment. TheRLC transmission mode mapping information for each V2X service maycorrespond to an RLC transmission mode (RLC AM or RLC UM) indicatormapped to a transmission type (unicast, groupcast, and broadcast). TheRLC transmission mode mapping information for each V2X service maycorrespond to an RLC transmission mode indicator mapped to a V2X serviceprofile. If the terminal obtains RLC configuration information forsidelink unicast transmission/reception through the V2X servicebroadcast message according to a determination in the operationindicated by the number (3), the terminal may perform a sidelink unicastoperation in an operation indicated by the number (5) by using thereceived RLC transmission mode and RLC configuration information. If theterminal fails to obtain RLC configuration information for sidelinkunicast transmission/reception through the V2X service broadcast messageaccording to a determination in the operation indicated by the number(3), the terminal may perform a sidelink unicast operation in anoperation indicated by the number (4) by using pre-configured RLCconfiguration information. The pre-configured RLC configurationinformation may include at least one of an RLC transmission mode mappedto a transmission type (unicast, groupcast, and broadcast), an RLCtransmission mode mapped to a V2X service identifier, an RLCtransmission mode mapped to a V2X application identifier, an RLCtransmission mode mapped to a V2X destination identifier, an RLCtransmission mode mapped to a V2X source identifier, configurationinformation of RLC AM, configuration information of RLC UM, packettransmission/reception resource information of RLC AM, ARQ feedbacktransmission/reception resource information of RLC AM, and packettransmission/reception resource information of RLC UM.

According to an embodiment, a transmission terminal may obtain, througha V2X service broadcast message transmitted by a base station, at leastone of sidelink unicast resource information according to an RLCtransmission mode, configuration information for transmission accordingto the RLC transmission mode, and configuration information required tobe shared by the transmission terminal and a reception terminalaccording to the RLC transmission mode.

According to an embodiment, a reception terminal may obtain, through aV2X service broadcast message transmitted by a base station, at leastone of sidelink unicast resource information according to an RLCtransmission mode, configuration information for reception according tothe RLC transmission mode. ARQ feedback configuration information, andARQ feedback resource information.

According to an embodiment, a transmission terminal may obtain, throughpre-configured RLC configuration information, at least one of sidelinkunicast resource information according to an RLC transmission mode,configuration information for transmission according to the RLCtransmission mode, and configuration information required to be sharedby the transmission terminal and a reception terminal according to theRLC transmission mode.

According to an embodiment, a reception terminal may obtain, throughpre-configured RLC configuration information, at least one of sidelinkunicast resource information according to an RLC transmission mode,configuration information for reception according to the RLCtransmission mode, ARQ feedback configuration information, and ARQfeedback resource information.

According to an embodiment, a reception terminal may obtain at least oneof sidelink unicast resource information according to an RLCtransmission mode randomly configured by the terminal, configurationinformation for reception according to the RLC transmission mode, ARQfeedback configuration information, and ARQ feedback resourceinformation.

According to an embodiment, a transmission terminal performing sidelinkunicast transmission or reception of a packet may transfer, to areception terminal, at least one of sidelink unicast resourceinformation according to an RLC transmission mode and configurationinformation required to be shared by the transmission terminal and areception terminal according to the RLC transmission mode, which areobtained through a V2X service broadcast message transmitted by a basestation or obtained through pre-configured RLC configurationinformation.

According to an embodiment, a reception terminal performing sidelinkunicast transmission or reception of a packet may transfer, to atransmission terminal, at least one of sidelink unicast resourceinformation according to an RLC transmission mode, configurationinformation required to be shared by the transmission terminal and thereception terminal according to the RLC transmission mode, ARQ feedbackconfiguration information, and ARQ feedback resource information, whichare obtained through a V2X service broadcast message transmitted by abase station or obtained through pre-configured RLC configurationinformation.

A V2X service broadcast message transmitted by a base station supportinga V2X service may include at least one of an RLC transmission modeindicator for each transmission type (unicast, groupcast, andbroadcast), an RLC transmission mode indicator mapped to a V2X serviceprofile, configuration information of RLC AM, configuration informationof RLC UM, packet transmission/reception resource information of thecase where RLC AM is configured, ARQ feedback transmission/receptionresource information of the case where RLC AM is configured, and packettransmission/reception resource information of the case where RLC UM isconfigured, according to an embodiment.

V2X services supported by a base station may vary according to RAT type.For example, a basic safety service is supported by 4G RAT (4G Uuinterface and 4G sidelink interface) and an advanced service may besupported by 5G RAT (5G Uu interface and 5G sidelink interface). A basicsafety service identifier may be mapped to a 4G RAT profile and anadvanced service identifier may be mapped to a 5G RAT profile.

A base station may transmit, through a service broadcast message (SIB),a RAT type, a basic safety service support indicator, an advancedservice support indicator, an LTE indicator, a new radio (NR) indicator,V2X RAT version information, a RAT bitmap supported by the base station,and the like, so as to notify of a service for which sidelinkcommunication is supported by the base station. In another embodiment, abase station may transmit 4G V2X SIB (information for basic safetyservice) or 5G V2X SIB (information for advanced service). If a terminalis in the coverage of the base station, the terminal may obtain, througha service broadcast message (SIB) transmitted by the base station, a RATtype, a basic safety service support indicator, and an advanced servicesupport indicator to identify which V2X service the corresponding basestation provides. The terminal may receive 4G V2X SIB (information forbasic safety service) or 5G V2X SIB (information for advanced service)transmitted by the base station, so as to identify which V2X service thecorresponding base station provides. In another embodiment, the terminalmay determine that an area corresponds to a basic safety service area oran advanced service area, by using service frequency band information ofthe base station. If the terminal is not located in the coverage of thebase station, the terminal may determine sidelink RAT for each serviceby using pre-configured information. The pre-configured information mayinclude basic safety service/advanced service mapping informationcorresponding to a service frequency band and RAT type informationcorresponding to a basic safety service or an advanced service.

If the terminal is in the coverage of the base station, the terminal mayreceive, from the base station, resource information and configurationinformation for transmitting a packet generated in an application layerof the terminal. Therefore, on the basis of a service type (basic safetyservice and advanced service) generated in the application layer of theterminal and V2X RAT type information supported by the base station fromwhich the terminal receives service, the terminal may determine whetherto request, from the base station, resource information andconfiguration information required for transmitting a generated servicepacket or use pre-configured information. If the base station supportsboth two V2X RAT types, the terminal may transmit service typeinformation the terminal needs, to the base station so as to receive,from the base station, resource information and configurationinformation required for transmitting the service packet.

4G RAT or 4G V2X of the disclosure may be based on a LTE-V2X technology,and 5G RAT or 5G V2X may be based on a NR-V2X technology.

FIGS. 12A and 12B illustrate a signal flow diagram between a terminaland a base station which exchange RAT information according to a V2Xservice type according to various embodiments. Referring to (12-1) inFIG. 12, (1) a base station supporting a V2X service may transmit a V2Xservice broadcast message (SIB). According to an embodiment, the V2X SIBmessage may include at least one of whether a basic safety V2X serviceis supported by the base station, whether an advanced service issupported thereby, RAT type information, an LTE indicator, an NRindicator, version information for each RAT, and a RAT bitmap supportedby the base station. In another embodiment, whether a basic V2X serviceis supported may be informed by transmitting an LTE-V2X SIB. Whether anadvanced V2X service is supported may be informed by transmitting anNR-V2X SIB. (2) If a basic V2X safety service is generated, the terminalmay determine whether the base station supports the basic V2X safetyservice, on the basis of information transmitted by the V2X SIB. If itis determined that the base station supports the basic V2X safetyservice, the terminal may transmit a UE assistance information messageincluding information (destination identifier, service identifier, QoSinformation, etc.) relating to the basic V2X safety service. (3) Thebase station may receive the UE assistance information message and thentransmit, to the terminal, an RRC configuration message includingconfiguration information (packet transmission/reception resourceinformation, scheduling information, LTE V2X mode 3 configuration andresource information, LTE V2X mode 4 configuration and resourceinformation, etc.) required for using the basic V2X safety service.

Referring to (12-2) in FIG. 12, (1) a base station supporting a V2Xservice may transmit a V2X service broadcast message (SIB). According toan embodiment, the V2X SIB message may include at least one of whether abasic V2X safety service is supported by the base station, whether anadvanced service is supported thereby, RAT type information, an LTEindicator, an NR indicator, version information for each RAT, and a RATbitmap supported by the base station. In another embodiment, whether abasic V2X service is supported may be informed by transmitting anLTE-V2X SIB. Whether an advanced V2X service is supported may beinformed by transmitting an NR-V2X SIB. (2) If an advanced V2X serviceis generated, the terminal may determine whether the base stationsupports the advanced V2X service, on the basis of informationtransmitted by the V2X SIB. If it is determined that the base stationsupports the advanced V2X service, the terminal may transmit a UEassistance information message including information (destinationidentifier, service identifier, QoS information, etc.) relating to theadvanced V2X service. (3) The base station may receive the UE assistanceinformation message and then transmit, to the terminal, an RRCconfiguration message including configuration information (packettransmission/reception resource information, scheduling information, NRV2X mode 1 resource and configuration information, NR V2X mode 2resource and configuration information, etc.) required for using theadvanced V2X service.

If the terminal fails to receive a V2X service SIB from the basestation, the terminal may request, from the base station, V2X RATconfiguration information required for V2X packet transmission orreception. In an embodiment, the terminal may randomly transmit, to thebase station, UE assistance information including V2X service typeinformation (a basic V2X service ID, an advanced V2X service ID, a basicV2X service indicator, an advanced V2X service indicator, and an QoSindicator). In another embodiment, the terminal may determine whether totransmit a UE assistance information message to the base station and V2Xservice type information (a basic V2X service ID, an advanced V2Xservice ID, a basic V2X service indicator, an advanced V2X serviceindicator, and an QoS indicator) to be included in the UE assistanceinformation message, on the basis of information such assistance aservice frequency of the base station, and a cell (an LTE cell or an NRcell) in which the base station is installed. If the terminal decidesnot to transmit a UE assistance information message, that is, if it isdetermined that the serving base station of the terminal provides a RATwhich does not support a V2X service type desired by the terminal, theterminal may use pre-configured resource information for basic V2Xservices or pre-configured resource information for advanced V2Xservices, according to V2X service type information.

If the terminal has received a V2X service SIB from the base station,but the terminal determines that V2X RAT configuration informationrequired for V2X packet transmission or reception is not included in theV2X service SIB, the terminal may request, from the base station, theV2X RAT configuration information required for V2X packet transmissionor reception. An operation of requesting V2X RAT configurationinformation by the terminal may include at least one of the embodimentsillustrated in FIGS. 12A and 12B.

FIG. 13 illustrates an operation of obtaining V2X configurationinformation, based on RAT information according to a V2X service type bya terminal which is in an RRC-connected state, according to variousembodiments. In an RRC-connected state, the terminal may generallyobtain V2X configuration information according to a V2X service type byexchanging an RRC dedicated message between the terminal and a basestation. Referring to FIG. 13, (1) if a V2X service is started in anapplication layer of the terminal, (2) the terminal may determinewhether the V2X service is a basic V2X service. If the terminaldetermines that the V2X service is the basic V2X service, according to aresult of the operation indicated by the number (2), the terminal mayidentify whether the terminal is in a base station area supporting thebasic V2X service, in an operation indicated by the number (3).

A method for determining the base station area supporting the basic V2Xservice in the operation indicated by the number (3) may correspond toat least one among the following methods.

i. The case where the base station is determined to an LTE base station(a base station installed in an LTE service frequency and a base stationinstalled in an LTE cell)

ii. The case where the base station broadcasts information indicatingthat the base station supports the basic V2X service (a basic V2Xservice indicator, basic V2X service frequency information, a basic V2Xservice resource pool, a basic V2X service SIB, an LTE V2X SIB, etc.)

If the terminal is in the base station area supporting the basic V2Xservice according to a result of the operation indicated by the number(3), (4) the terminal may transmit a UE assistance information messageto the base station to request resource and configuration informationrequired for the basic V2X service. The UE assistance informationmessage may include at least one of a basic V2X service identifier, adestination identifier, and QoS information. (5) The terminal mayreceive an RRC configuration message from the base station in responseto the UE assistance information message, and may identify whether theresource and configuration information for the basic V2X service isreceived. If the terminal receives the resource and configurationinformation for the basic V2X service from the base station in theoperation indicated by the number (5), (6) the terminal may use thebasic V2X service by using the obtained information.

If the terminal is not located in the base station area supporting thebasic V2X service according to a determination of the operationindicated by the number (3), (7) the terminal may obtain the resourceand configuration information required for the basic V2X service frompre-configured configuration information. If the terminal fails toreceive the resource and configuration information for the basic V2Xservice from the base station according to a determination of theoperation indicated by the number (5), the terminal may perform anoperation indicated by the number (7). An embodiment of a method fordetermining that the base station does not provide the resource andconfiguration information for the basic V2X service in the operationindicated by the number (5) may include at least one of the followingcontents.

i. The base station transmits an RRC message including pre-configuredbasic V2X service resource and configuration information (pre-configuredinformation use indicator and pre-configured resource information).

ii. The terminal fails to receive an RRC configuration message includingbasic V2X service resource and configuration information from the basestation within a predetermined time interval after the operationindicated by the number (4).

iii. The base station transmits an RRC message including indicationinformation indicating that the base station is unable to provideresource and configuration information for the basic V2X service.

According to a result in the operation indicated by the number (2), ifthe terminal determines that the V2X service is an advanced V2X service,the terminal may identify that the terminal is located in a base stationarea supporting the advanced V2X service, in an operation indicated bythe number (8).

A method for determining the base station area supporting the advancedV2X service in the operation indicated by the number (8) may correspondto at least one among the following methods.

i. The case where the base station is determined to an NR base station(a base station installed in an NR service frequency and a base stationinstalled in an NR cell)

ii. The case where the base station broadcasts information (an advancedV2X service indicator, advanced V2X service frequency information, anadvanced V2X service resource pool, an advanced V2X service SIB, an NRV2X SIB, etc.) indicating that the base station supports the advancedV2X service

If the terminal is in the base station area supporting the advanced V2Xservice according to a result of the operation indicated by the number(8), (9) the terminal may transmit a UE assistance information messageto the base station to request resource and configuration informationrequired for the advanced V2X service. The UE assistance informationmessage may include at least one of an advanced V2X service identifier,a destination identifier, and QoS information. (10) The terminal mayreceive an RRC configuration message from the base station in responseto the UE assistance information message, and may identify whether theresource and configuration information for the advanced V2X service isreceived. If the terminal receives the resource and configurationinformation for the advanced V2X service from the base station in theoperation indicated by the number (10), (11) the terminal may use theadvanced V2X service by using the obtained information.

If the terminal is not located in the base station area supporting theadvanced V2X service according to a determination of the operationindicated by the number (8), (12) the terminal may obtain the resourceand configuration information required for the advanced V2X service frompre-configured configuration information. If the terminal fails toreceive the resource and configuration information for the advanced V2Xservice from the base station according to a determination of theoperation indicated by the number (10), the terminal may perform anoperation indicated by the number (12). An embodiment of a method fordetermining that the base station does not provide the resource andconfiguration information for the advanced V2X service in the operationindicated by the number (10) may include at least one of the followingcontents.

i. The base station transmits an RRC message including pre-configuredadvanced V2X service resource and configuration information(pre-configured information use indicator and pre-configured resourceinformation).

ii. The terminal fails to receive an RRC configuration message includingadvanced V2X service resource and configuration information from thebase station within a predetermined time interval after the operationindicated by the number (9).

iii. The base station transmits an RRC message including indicationinformation indicating that the base station is unable to provideresource and configuration information for the advanced V2X service.

FIG. 14 illustrates an operation of obtaining V2X configurationinformation, based on RAT information according to a V2X service type bya terminal which is in an RRC-disconnected state, according to variousembodiments. In an RRC-disconnected state, the terminal may generallyobtain V2X configuration information according to a V2X service type byreceiving a V2X SIB message transmitted by a base station throughbroadcast. Referring to FIG. 14, (1) if a V2X service is started in anapplication layer of the terminal, (2) the terminal may determinewhether the V2X service is a basic V2X service. If the terminaldetermines that the V2X service is the basic V2X service, according to aresult of the operation indicated by the number (2), the terminal mayidentify whether the terminal is in a base station area supporting thebasic V2X service, in an operation indicated by the number (3).

A method for determining the base station area supporting the basic V2Xservice in the operation indicated by the number (3) may correspond toat least one among the following methods.

i. The case where the base station is determined to an LTE base station(a base station installed in an LTE service frequency and a base stationinstalled in an LTE cell)

ii. The case where the base station broadcasts information indicatingthat the base station supports the basic V2X service (a basic V2Xservice indicator, basic V2X service frequency information, a basic V2Xservice resource pool, a basic V2X service SIB, an LTE V2X SIB, etc.)

If the terminal is in the base station area supporting the basic V2Xservice according to a result of the operation indicated by the number(3), (4) the terminal may use basic V2X service resource andconfiguration information included in the V2X SIB message transmitted bythe base station. If the terminal is not located in the base stationarea supporting the basic V2X service according to a determination inthe operation indicated by the number (3), (5) the terminal may obtainresource and configuration information required for the basic V2Xservice from pre-configured configuration information.

A case where resource and configuration information for the basic V2Xservice is not included in the V2X SIB message transmitted by the basestation in the operation indicated by the number (4) is also possible.In this case, the terminal may perform the operation indicated by thenumber (5). An embodiment allowing a determination that the resource andconfiguration information for the basic V2X service is not included inthe V2X SIB message may include at least one of the following contents.

i. The base station transfers a V2X SIB message including pre-configuredbasic V2X service resource and configuration information (pre-configuredinformation use indicator and pre-configured resource information). ii.The base station does not transmit an SIB message including the basicV2X service resource and configuration information.

According to a result in the operation indicated by the number (2), ifthe terminal determines that the V2X service is an advanced V2X service,the terminal may identify that the terminal is located in a base stationarea supporting the advanced V2X service, in an operation indicated bythe number (6).

A method for determining the base station area supporting the advancedV2X service in the operation indicated by the number (6) may correspondto at least one among the following methods.

i. The case where the base station is determined to an NR base station(a base station installed in an NR service frequency and a base stationinstalled in an NR cell)

ii. The case where the base station broadcasts information (an advancedV2X service indicator, advanced V2X service frequency information, anadvanced V2X service resource pool, an advanced V2X service SIB, an NRV2X SIB, etc.) indicating that the base station supports the advancedV2X service

If the terminal is in the base station area supporting the advanced V2Xservice according to a result of the operation indicated by the number(6), (7) the terminal may use advanced V2X service resource andconfiguration information included in the V2X SIB message transmitted bythe base station. If the terminal is not located in the base stationarea supporting the advanced V2X service according to a determination inthe operation indicated by the number (6), (8) the terminal may obtainresource and configuration information required for the advanced V2Xservice from pre-configured configuration information.

A case where resource and configuration information for the advanced V2Xservice is not included in the V2X SIB message transmitted by the basestation in the operation indicated by the number (7) is also possible.In this case, the terminal may perform the operation indicated by thenumber (8).

An embodiment of a method for determining that the base station does notprovide the resource and configuration information for the advanced V2Xservice in the operation indicated by the number (7) may include atleast one of the following contents.

(1) The base station transfers an SIB message including pre-configuredadvanced V2X service resource and configuration information(pre-configured information use indicator and pre-configured resourceinformation).

(2) The base station does not transmit an SIB message including theadvanced V2X service resource and configuration information.

Next, referring to FIG. 15, a method for exchanging informationindicating bi-directional sidelink traffic during a procedure ofconfiguring a connection for sidelink unicast between a terminal 120 anda terminal 130, and according thereto, obtaining configurationinformation for sidelink unicast-based transmission or reception of apacket will be explained. If two terminals transmit or receivebi-directional sidelink traffic to or from each other,transmission-specific configuration information, configurationinformation required to be exchanged between a transmission terminal anda reception terminal, and reception-specific configuration informationmay be identically configured in a case where the terminals 120 and 130serve as transmission terminals and in a case where the terminals 120and 130 serve as reception terminals. In these cases, one terminal amongthe terminals 120 and 130 may obtain SLRB connection configurationinformation corresponding to the bi-directional sidelink traffic and mayshare the obtained SLRB connection configuration information with theopposite terminal.

FIG. 15 illustrates an operation of processing sidelink unicastconfiguration information by a terminal according to an embodiment.

Referring to FIG. 15, the terminal 120 may transmit a connectionconfiguration message for sidelink unicast, in an operation indicated bythe number (1). The message transmitted in the operation indicated bythe number (1) may include at least one of a PC5-S message or a PC5-RRCmessage. The message transmitted in the operation indicated by thenumber (1) may include information indicating a sidelink unicastconnection configuration for transmission or reception of bi-directionalsidelink traffic. The terminal 130 may transmit a response message ofthe connection configuration message for sidelink unicast which istransmitted by the terminal 120, in the operation indicated by thenumber (2). The message transmitted in the operation indicated by thenumber (2) may include at least one of a PC5-S message or a PC5-RRCmessage. The message transmitted in the operation indicated by thenumber (2) may include information indicating a sidelink unicastconnection configuration for transmission or reception of bi-directionalsidelink traffic. The terminal 120 may be configured to function toobtain configuration information of a sidelink unicast connection fortransmission or reception of the bi-directional sidelink traffic, in theoperation indicated by the number (3). The embodiment illustrated inFIG. 15 illustrates a case where the terminal 120 obtains connectionconfiguration information for transmission or reception ofbi-directional sidelink traffic, but the terminals may exchangeinformation indicating a terminal functioning to obtain connectionconfiguration information for transmission or reception ofbi-directional sidelink traffic, in the procedure indicated by thenumber (1) or (2), and the terminal which will function to obtain theconnection configuration information may be determined according to theexchanged information. The terminal functioning to obtain connectionconfiguration information for transmission or reception ofbi-directional sidelink traffic may obtain at least one of sidelinkunicast transmission/reception resource information, configurationinformation for transmission according to an RLC transmission mode,configuration information required to be shared by a transmissionterminal and a reception terminal according to the RLC transmissionmode, and configuration information for reception according to the RLCtransmission mode according to the methods illustrated in FIGS. 5 to 11.For example, if the terminal 120 is determined to be in the coverage ofa base station, the terminal 120 may obtain the configurationinformation from the base station. If the terminal 120 is locatedoutside a base station coverage, the terminal 120 may obtainpre-configured configuration information. For example, a part of theconfiguration information may be randomly configured by the terminal120. The terminal 120 may transfer the obtained sidelink unicastconfiguration information to the terminal 130, in the operationindicated by the number (4). The terminal 130 may obtain the sidelinkunicast configuration information from the terminal 120 and thentransfer an identification message to the terminal 120 in response tothe information, in an operation indicated by the number (5).

Although not illustrated in FIG. 15, whether the method of obtainingconnection configuration information for transmission or reception ofbi-directional sidelink traffic as illustrated in FIG. 15 is supportedmay be indicated by a base station, or may be notified of the basestation by a terminal and then indicated by the base station.

Methods according to embodiments stated in claims and/or disclosedherein may be implemented in hardware, software, or a combination ofhardware and software.

When the methods are implemented by software, a computer-readablestorage medium for storing at least one program (software module) may beprovided. The at least one program stored in the computer-readablestorage medium may be configured for execution by at least one processorwithin an electronic device. The at least one program may includeinstructions that cause the electronic device to perform the methodsaccording to embodiments as defined by the appended claims and/ordisclosed herein.

The at least one program (software modules or software) may be stored innon-volatile memories including a random access memory and a flashmemory, a read only memory (ROM), an electrically erasable programmableread only memory (EEPROM), a magnetic disc storage device, a compactdisc-ROM (CD-ROM), digital versatile discs (DVDs), or other type opticalstorage devices, or a magnetic cassette. Alternatively, any combinationof some or all of the memories may form a memory in which the program isstored. Further, a plurality of such memories may be included in theelectronic device.

In addition, the at least one program may be stored in an attachablestorage device which is accessible through a communication network suchas the Internet, Intranet, local area network (LAN), wide area network(WAN), and storage area network (SAN), or a combination thereof. Such astorage device may access a device performing embodiments via anexternal port. Further, a separate storage device on the communicationnetwork may access a device performing embodiments.

In the above-described detailed embodiments, an element included in thedisclosure is expressed in the singular or the plural according to adetailed embodiment. However, the singular form or plural form isselected for convenience of description, suitable for the presentedsituation, and the disclosure is not limited to a single element ormultiple elements thereof. Further, either multiple elements expressedin the description may be configured into a single element or a singleelement in the description may be configured into multiple elements.

While the detailed description in the disclosure has been shown withreference to certain embodiments thereof, it will be understood thatvarious changes can be made therein without departing from the scope ofthe disclosure. Therefore, the scope of the disclosure should not bedefined as being limited to the described embodiments, but should bedefined by the appended claims and equivalents thereof.

1. An operation method of a first terminal, the method comprising:transmitting a first message to a base station; receiving, from the basestation, a second message including configuration information related toa transmission mode based on the first message; and transmitting, to asecond terminal, a third message corresponding to the second message,wherein the first message includes at least one of unicast sessioninformation, transmission mode type information, service QoSinformation, and preferred radio link control (RLC) mode information ofthe first terminal.
 2. The method of claim 1, wherein the transmissionmode corresponds to at least one of unicast, groupcast, and broadcast.3. The method of claim 1, wherein the configuration information issidelink RLC configuration information.
 4. An operation method of a basestation, the method comprising: receiving a first message from a firstterminal; determining a transmission mode, based on the first message;and transmitting, to the first terminal, a second message includingconfiguration information related to the transmission mode, wherein thefirst message includes at least one of unicast session information,transmission mode type information, service QoS information, andpreferred radio link control (RLC) mode information of the firstterminal.
 5. The method of claim 4, wherein the transmission modecorresponds to at least one of unicast, groupcast, and broadcast.
 6. Themethod of claim 4, wherein the configuration information is sidelink RLCconfiguration information.
 7. An operation method of a second terminal,the method comprising: receiving, from a first terminal, a third messagecorresponding to a second message received from a base station, whereinthe second message includes configuration information related to atransmission mode determined based on at least one of unicast sessioninformation, transmission mode type information, service QoSinformation, and preferred radio link control (RLC) mode information ofthe first terminal.
 8. The method of claim 7, wherein the transmissionmode corresponds to at least one of unicast, groupcast, and broadcast.9. A first terminal in a wireless communication system, the firstterminal comprising: a transceiver unit; and a control unit connected tothe transceiver unit, the control unit is configured to: transmit afirst message to a base station; receive, from the base station, asecond message including configuration information related to atransmission mode based on the first message; and transmit, to a secondterminal, a third message corresponding to the second message, andwherein the first message includes at least one of unicast sessioninformation, transmission mode type information, service QoSinformation, and preferred radio link control (RLC) mode information ofthe first terminal.
 10. The first terminal of claim 9, wherein thetransmission mode corresponds to at least one of unicast, groupcast, andbroadcast.
 11. The first terminal of claim 9, wherein the configurationinformation is sidelink RLC configuration information.
 12. A basestation in a wireless communication system, the base station comprising:a transceiver unit; and a control unit connected to the transceiverunit, the control unit is configured to: receive a first message from afirst terminal; determine a transmission mode, based on the firstmessage; and transmit, to the first terminal, a second message includingconfiguration information related to the transmission mode, and whereinthe first message includes at least one of unicast session information,transmission mode type information, service QoS information, andpreferred radio link control (RLC) mode information of the firstterminal.
 13. The base station of claim 12, wherein the transmissionmode corresponds to at least one of unicast, groupcast, and broadcast.14. The base station of claim 12, wherein the configuration informationis sidelink RLC configuration information.
 15. A second terminal in awireless communication system, the second terminal comprising: atransceiver unit; and a control unit connected to the transceiver unit,the control unit is configured to: receive, from a first terminal, athird message corresponding to a second message received from a basestation, and wherein the second message includes configurationinformation related to a transmission mode determined based on at leastone of unicast session information, transmission mode type information,service QoS information, and preferred radio link control (RLC) modeinformation of the first terminal.